In the hydrodesulfurization of petroleum hydrocarbonaceous oils, cobalt-molybdenum or nickel-molybdenum hydrotreating catalysts comprising one or more metals selected from metals of Groups VIII and VI of the Periodic Table of the Elements supported on an alumina or silica-alumina carrier have been widely used.
It is highly desirable that such catalysts, and the preparation thereof, be such that a relatively large amount of cobalt-molybdenum or nickel-molybdenum particles are substantially homogeneously dispersed on a support material. The inventors hereof have found that when cobalt or nickel is deposited on a silica-alumina carrier by an ion exchange method in a first step, and molybdenum is deposited thereon in the second step, molybdenum as the main component can be supported on the carrier in a uniformly dispersed state to form a highly active catalyst.
The inventors have also found that catalytic activity for hydrodesulfurization can be further improved by controlling the pore distribution in the catalyst in a specified range. Both concepts are disclosed in U.S. Ser. No. 726,112, filed Apr. 23, 1985, which is incorporated herein by reference.
While such catalysts have met with various degrees of success, there is still a need in the art for further improvement, such as improving the catalysts' desulfurization and denitrogenation properties.